1. Field of the Invention
The present invention relates to a method for manufacturing a cylinder interior fuel injection valve for directly injecting fuel into a combustion chamber of an internal combustion engine, and an apparatus for adjusting a fuel injection amount used therefor.
2. Description of the Related Art
FIG. 6 is a cross-sectional view showing a cylinder interior fuel injection valve.
In FIG. 6, a cylinder interior fuel injection valve 1 is composed of a housing body 2 and a valve assembly 3 fixed to one end of the housing body 2 by press-fitting or the like and covered by a sleeve 35. A fuel supply pipe (not shown) is connected to the other end of the housing body 2 for supplying pressurized fuel from the fuel supply pipe through a filter 37 into the cylinder interior fuel injection valve 1.
The housing body 2 is provided with a first housing 30 having a flange 30a for mounting the cylinder interior fuel injection valve 1 on a cylinder head (not shown) of an internal combustion engine, and a second housing 40 on which a solenoid assembly 50 is mounted. The solenoid assembly 50 is provided with a bobbin 52 around which a coil 51 is wound and a core 53 installed in an inner circumferential portion of the bobbin 52. A winding of the coil 51 is connected to a terminal 56. The core 53 is formed into a hollow cylindrical shape so that its interior serves as a fuel passage. A valve closing spring 55 is interposed and compressed between an adjuster 54 and a needle valve 12 in the hollow cylindrical portion. An armature 31 is mounted at the other end of the needle valve 12 so as to face to a tip end of the core 53. Disposed in an intermediate portion of the needle valve 12 are a guide 12a for sliding and guiding the valve 12 along the inner circumferential surface of a valve body 9 and a needle flange 12b which is in contact with a spacer 32 disposed in the first housing 30. The housing body 2 constitutes a housing of the cylinder interior fuel injection valve 1 in cooperation with the sleeve 35.
The valve assembly 3 is provided with a stepped hollow cylindrical valve main body 9 having a small diameter portion 7 and a large diameter portion 8, a valve seat 11 having a fuel injection port 10 and fixed to a tip end of a center hole within the valve main body 9, a needle valve 12 serving as a valve body for being seated on or separated away from the seat 11 by the solenoid assembly 50 for opening and closing the fuel injection port 10, and a swirl member 13 for guiding the needle valve 12 in an axial direction while imparting a swirl motion to the fuel to be introduced into the fuel injection port 10 of the seat 11 in a radially inward direction.
Here, the first housing 30, the core 53 and the armature 31 are made of magnetic material, for example, electromagnetic stainless steel to form a magnetic circuit.
The tip end side of the thus constructed cylinder interior fuel injection valve 1 is inserted into a fuel injection insertion hole (not shown) provided in the cylinder head, a retainer jig (not shown) is applied to the flange 30a from the outside, and the retainer jig is securely fastened to the cylinder head by mounting bolts (not shown). A flat washer or a corrugated washer is interposed between the cylinder interior fuel injection valve 1 and the cylinder head and a seal between the cylinder interior fuel injection valve 1 and the cylinder head is maintained by a pressure of the retainer jig in the axial direction. Also, a mounting hole of the fuel supply pipe is fitted and fixed to an O-ring portion for sealing the upper portion of the cylinder interior fuel injection valve 1.
Then, the electric application to the coil 51 is controlled so that the needle valve 12 is moved in the axial direction to open/close the fuel injection port 10.
Then, when the fuel injection port 10 is open, the pressurized fuel fed from the fuel supply pipe is caused to pass through the fuel passage in the interior of the core 53 and is subjected to the swirl energy by the swirl member 13 to be atomized and injected from the fuel injection port 10 into the combustion chamber.
A method for manufacturing the conventional cylinder interior fuel injection valve 1 will now be described with reference to FIG. 7.
In the method for manufacturing the conventional cylinder interior fuel injection valve 1, it is necessary to adjust the fuel injection amount so that it falls within a range of a rated value. The fuel injection amount adjusting step is carried out before the fixture of the adjuster 54 to the core 53. As shown in FIG. 8, under the condition that the fuel filter 37 is removed away, an adjusting pin 18 inserted from the fuel supply side is inserted or retracted so that the axial position of the adjuster 54 is adjusted to change the compression amount of the valve closing spring 55 to adjust the fuel injection amount.
Namely, the adjusting pin 18 inserted from the fuel supply side is moved in the axial direction to adjust the position of the adjuster 54 (step 100), and at this time, the fuel injection amount is measured (step 101). It is then judged whether or not the measured value of the fuel injection amount falls within the rated range (step 102). If the measured value of the fuel injection amount falls within the rated range, the core 53 is press-fitted from the outside. The adjuster 54 is fixed to the core 53 (step 103) to finish the fuel injection amount adjusting step. The process moves to the next step (step 104). Also, if the measured value of the fuel injection amount does not fall within the rated range, the process is returned back to step 100, and the position of the adjuster 54 is adjusted again so that the fuel injection amount falls within the rated range.
The following function in addition to the function of adjusting the fuel injection amount as described above is required for the spring force of the valve closing spring 55 in such a kind of the cylinder interior fuel injection valve 1.
First, the cylinder interior fuel injection valve 1 faces to the combustion chamber of the internal combustion engine and the combustion gas pressure of the combustion chamber is applied to the needle valve 12 in the valve opening direction. It is necessary to set a lower limit to the spring force of the valve closing spring 55 so that the needle valve 12 is seated on the valve seat 11 to maintain the valve closed condition and the introduction of the combustion gas into the cylinder interior fuel injection valve 1 is prevented even if the combustion gas pressure is applied to the needle valve 12 in the non-application of the current to the coil 51.
Secondly, the magnetic suction force of the solenoid assembly 50 has to be greater than the sum of the force in the valve closing direction by the spring force of the valve closing spring 55 and the force in the valve closing direction by the fuel pressure in order to open the needle valve 12 in the electric application to the coil 51. The fuel pressure used in such a kind of a cylinder interior fuel injection valve 1 is high in comparison with the conventional fuel injection valve, and the force in the valve closing direction by the fuel pressure is also high. However, the excessively increasing the suction force of the solenoid assembly 50 for coping with this would raise the problems in size, heat generation and cost. Accordingly, an upper limit has to be set for the spring force of the valve closing spring 55, and the needle valve 12 has to be opened to inject fuel upon the electric application to the coil 51 within the fuel pressure range which would be generated in the actual product.
However, in the adjusting step of the fuel injection amount in the manufacturing method of the conventional cylinder interior fuel injection valve 1, the positional adjustment of the adjuster 54 is repeated so that the fuel injection amount is the target value, and when the fuel injection amount is the target value, the core 53 is press-fitted to adjuster 54 which is thereby fixed to the core 53. Accordingly, the spring force of the valve closing spring 55 of the cylinder interior fuel injection valve 1 that has been produced is unknown. In other words, in the conventional manufacturing method, since the spring force of the valve closing spring 55 is not controlled, there is a problem that the combustion gas would be introduced into the interior of the fuel injection valve to generate the air engagement due to the fluctuation in the combustion gas pressure or the fuel pressure that would occur when the fuel injection valve is mounted on the actual engine, or the needle valve 12 would not be opened upon the electric application to the coil so that the predetermined fuel injection amount could not be obtained.